Before we go any further we should probably point out that ‘Blue John’ is not a person – it’s a rather gorgeous mineral that’s found in the ground in the Peak District.

It was the Romans who first discovered the stuff, about 2,000 years ago, and by all accounts they were rather fond of it; vases made out of Blue John stone were found when they excavated the ruins of Pompeii – in Italy…Why not take your own journey to the centre of the earth, to see what all the fuss is about? An expert guide will give you a tour of the vast underground cavern just outside the town of Castleton, where miners still dig the mineral from the earth mostly by hand.

The ceilings are covered in stalagmites (or is that stalactites?), which have formed from years of erosion and water flowing through the tunnels – long before humans were here, of course.

Keep an eye out for fossils of sea creatures, too; this area was once underwater…